This invention relates to a method of forming a drawn and redrawn container body from a metal blank. More particularly, it relates to a method of preventing wrinkles during forming of the bottom end wall of a drawn and redrawn container body.
It is well known to draw and iron a sheet metal blank to make a thin-walled can body for packaging carbonated beverages. It is also well known that metal manufacturers, can makers and carbonated beverage packagers have had and continue to have a goal to reduce the weight of the container and thereby reduce the cost of packaging. At least one way to reduce weight is to form a profile in the bottom end wall which is capable of strengthening the end wall's resistance against buckling from internal pressure. By so doing, thinner metal can be used to make the can and thereby reduce weight and cost. U.S. Pat. Nos. 3,905,507; 4,099,475; 4,151,927; 4,177,746 and 4,294,373 are but a few of the many which are concerned with a bottom end wall profile or method of making such a profile.
Many of the end wall profiles include an annular portion which slopes generally inwardly and downwardly from the can sidewall and an inwardly projecting profiled portion, such as a dome, for example, circumscribed by such annular portion. The thinner the metal from which containers are made, the greater the tendency for the metal in the inwardly and downwardly projecting annular wall to wrinkle during redrawing and doming. Elert et al U.S. Pat. No. 4,372,143 is a patent which proposes a solution to this problem. The Elert et al solution involves adapting the apparatus used to form the dome so as to support the beveled annular wall with a pressure ring while the dome is being formed.